Systems that enable a user to record music for playback or for producing musical notation require that a tempo and a time signature for the music be supplied before the user can start recording. Once the user starts recording, he is constrained to play in time to a metronome click. This is an impediment to recording new ideas, as decisions about changes in tempo and time signature have to be made in advance and the user is unable to introduce timing variations that are a natural part of a performance. If the user opts to turn off the metronome click, he can record in an unconstrained manner, but the recording system is unable to interpret the musical data for quantization or displaying notation because the input is not aligned with an internal tempo map.
The requirement to pre-select a time signature and tempo is particularly difficult for less experienced users, who may not be familiar with music theory or even with musical notation. There is therefore a need for musical input systems that free users of this constraint.